In Distributed environment authentication and keyexchange mechanisms plays a major role. Generally in authentication a client and server agree upon a cryptographic key which is mutually exchanged. Earlier passwords were stored in a single server where if an intruder gains access of that server by some malicious attacks then all the passwords stored in the database are to be compromised and therefore the e-commerce application security is endangered. In-order to improve the efficiency and performance of the authentication mechanisms we involve multiple servers to store the passwords and participate in key-exchange and authentication process so as to ensure that even a single server is compromised the whole system's security is not in threat and also generating a nonce values randomly for every session corresponds to a two level security mechanism where the scope of an attacker to pretend as the legitimate user and login into the system is completely restricted.In this model the passwords are stored in their equivalent hash values and they are spitted into multiple servers. Making it even more difficult for the attacker to determine the password even by reverse engineering he cannot intercept the actual password form segments of hash value. Hence, we can present this model as safe and secure password based authentication scheme using key exchange mechanism.

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A&M&-Aprobabilistic method is presented wtdcb cryptanalyzes any N key cryptosystem in N2i3 operations with N2j3 words of memory (average vale) after a precomputatioo which requires N operations. If tke precomputation cao be performed in a reasooable time period (e.g* several years), the additional computation reqoired to recover e& key compares very favorably wltb the N operations reqdred by an exkaostive sear& and the N words of memory reqoircd by table lookup. When applied to the Data Enqption Standard (DES) osed lo block mode, it imlicatea tbat soluths should cost between $1 and $100 esck. Themethod worksinachosenplaintextattackand,itcipherbloekchainingisnotused, am also be osed in a ciphertext-only attack.

A "secret sharing system" permits a secret to be shared among n trustees in such a way that any k of them can recover the secret, but any k-1 have complete uncertainty about it. A linear coding scheme for secret sharing is exhibited which subsumes the polynomial interpolation method proposed by Shamir and can also he viewed as a deterministic version of Blakley's probabilistic method. Bounds on the maximum value of n for a given k and secret size are derived for any system, linear or nonlinear. The proposed scheme achieves the lower bound which, for practical purposes, differs insignificantly from the upper bound. The scheme may be extended to protect several secrets. Methods to protect against deliberate tampering by any of the trustees are also presented.